The present invention relates generally to a data collection system with remote units for telemetrically transferring data to a central processing location, and more particularly, to an automatic meter reading (AMR) system in which conventional subscriber telephone lines are used to transfer collected data (e.g., utility meter readings) from a customer""s premises to a central processor.
A traditional way to collect data from utility meters (e.g., gas, electric, water) at customer sites is to send a person to read the respective meters periodically. An automatic meter reading (AMR) system, as illustrated in FIGS. 1A and 1B, changes this labor intensive data collection procedure. With an AMR system, utility companies not only can reduce the number of necessary meter reading personnel, but also can get more information from the meters. For instance, an AMR system can be set to record the meter data every 15 minutes and store the data in memory. A processing center or host computer can then periodically retrieve and analyze the collected data, such that the information may be used to compile peak time and maximum usage statistics, to work with a customer to establish rates, to notify the customer if an abnormal usage is identified, and ultimately to provide better customer services.
Since telephone infrastructure has been established for many years and reaches almost every corner of the country, it is one of the logical choices to use as the AMR system communication means. A typical AMR system configuration is shown in FIG. 1A where a utility company (or meter reading service) utilizes a host computer system 4 to collect data from a plurality of consumers (homes, apartments, businesses, etc.) over the existing telephone system. In certain applications, the host computer system may be co-resident with a telephone central office switch 6 or it may be remotely located (as shown), appearing as just another subscriber telephone line 8 to the central office switch 6. At each consumption point, a telephone line telemetry device 10 is connected to one or more utility meters (not shown), thereby making the meters electronically accessible to a host computer system via the existing public telephone network.
As shown in more detail in FIG. 1B, the design of telemetry device 10 is such that it operates over the same telephone line 8 as the subscriber""s telephone set 12 so there is no need for additional phone lines or infrastructure. In AMR applications, the telemetry device 10 is called a meter interface unit (MIU) or telemetry interface unit (TIU), since the device serves as an interface between two different electrical environments. One side of MIU telemetry device 10, called the meter side, is connected to one or more utility meters 14, 16, 18, while the remaining side of the MIU is connected in parallel across the subscriber telephone line 8. With regard to the telephone-line-side of the MIU, the connection is electrically equivalent to the homeowner plugging in an additional telephone or answering machine, and telemetry device 10 appears in parallel with the other telephone devices 20 which are connected to the phone line. As shown in FIG. 1B, other than connecting MIU 10 to the subscriber line, no modification of the existing telephone line wiring is required.
The MIU telemetry device 10 can be designed to share the telephone line in a manner creating no interference for the customer. If a customer is using the phone 12 or the facsimile machine 20, the MIU device detects that the phone line 8 is not then available, and a call back to the host computer 4 (FIG. 1A) will not occur immediately, even though a scheduled call back time has been reached. Once the phone line becomes available, the device initiates a call to the host computer. The MIU dials automatically pursuant to a calling schedule and availability of the phone line, uploads the accumulated meter data to the host computer, and then turns itself off to again release the phone line. If the customer wants to use the phone while the MIU device is communicating with the host computer, the MIU immediately releases the phone line. As a result, the MIU is transparent to the customer during normal operation. Use by the MIU device of a toll-free 800 number to call the host computer and transfer meter data over the existing telephone line infrastructure further ensures that this is a zero impact event to the customer.
The AMR system just described is referred to as a dial-inbound system. The basic idea of dial-inbound is to let the MIU device initiate the call to the host computer (according to a call back schedule which is pre-programmed). At times, however, the utility company needs to know the meter reading immediately (such as when a customer moves out of a house) so they can prepare a final bill based on a final reading. To meet this requirement, an additional alert function is added to the dial-inbound MIU device. With this function, the MIU device will initiate a call to the host computer immediately after receiving an alert signal if a phone line is available. This is referred to typically as a dial-outbound function.
There are various ways to alert an MIU device. One way is to let the host computer 4 dial the MIU 10. If the number of rings exceeds a certain threshold number, the MIU device calls back after the phone line is available. It is tricky, however, to select this threshold number. If the number is too small, a normal phone call may trigger the MIU to initiate an unwanted call back. One the other hand, if the number is too large, say more than five, an answering machine 20 may activate before the number of rings ever reaches five, such that the MIU device cannot be alerted.
Another way to alert the MIU device is to use a special stream of data. Once a person or an answering machine picks up the phone, the host computer 4 sends out this special data stream. The MIU device 10 decodes the received data stream and, if the stream matches a predetermined alert code, the MIU will call back the host computer when the phone line is available. The data stream should be complex enough that normal voice and/or fax data streams will not trigger the MIU""s alert function. In conjunction with either the ring alert or the special data stream alert, the inbound MIU device must be capable of accepting a demand call.
Since the MIU device is physically connected both to utility meters and a telephone line, a certain breakdown voltage ( greater than 1,500V) is required between the telephone terminal and the meter terminals. The best way to electrically isolate the two sides is to use an optocoupler. Depending on the specific components utilized, the break down voltage can easily exceed 5 KV, which is higher than the U.S. and European safety requirements.
In this preferred design, when the telephone side of the MIU 10 is isolated by an optocoupler, the alert function circuitry on the telephone side cannot be powered by the meter-side power source (i.e., an AC power line connection or a battery). In order to avoid using a separate, additional battery for the telephone-side circuitry, the present invention uses the telephone ring pulses to provide the power necessary to support the alert function circuit. A low-powered microcontroller is employed in the telephone-side circuitry to decode the special data stream. When an alert data stream is identified, the telephone-side microcontroller sends out an alert trigger signal to a meter-side microcontroller through the optocoupler. The meter-side microcontroller then initiates a data-transmitting call to the host computer 4 as soon as the phone line 8 is available.
Accordingly, one object of the present invention is to provide a dial-inbound MIU telemetry device having the additional capability of being on-demand activated by a data signal, wherein data received in the activating signal instructs the MIU to open one or more selected meter interface ports.
Another object of the present invention is to provide such an MIU telemetry device having two inter-communicating, but electrically-isolated, circuit portions, one of which is connected to the telephone line and the other of which is connected to one or more utility meters.
Yet another object of the present invention is to provide such an MIU telemetry device having an optocoupler for achieving the electrically-isolated inter-communication between the respective MIU circuit portions.
A still further object of the present invention is to provide such an MIU telemetry device in which the telephone-side portion of the MIU circuitry is powered by the telephone ring pulses associated with the data signal.
In accordance with a preferred embodiment of the present invention, there is provided an MIU telemetry device for collecting information at a remote location and transmitting the information over a telephone line to a host station, the telemetry device including at least one meter port, a first microcontroller which collects information from the meter port(s) and transmits the collected information to the host station, a first power supply for powering the first microcontroller, a second microcontroller coupled to the telephone line but electrically isolated from the meter port(s), the first microcontroller and the first power supply, wherein the second microcontroller detects when data signals received from the host station contain an alert signal and, upon such detection, provides a trigger signal to the first microcontroller to initiate collection of information from the meter port(s), and a second power supply for the second microcontroller which derives energy from ring pulse signals received from the host station and at least temporarily stores the derived ring energy.